Why are my woofers pumping?

Nothing so bad it isn’t some good also. I am trying to find a way out, how to repair it for a reasonable cost. This should not happen, for a moderately used (not misused) cartridge. Such things - diamonds falling off, cantilevers breaking, cantilevers or diamonds not precisely tuned - are known to happen, across cart makers. As users we hope for better quality control and follow-up when sub-optimal units have been sold.

I think we now have a very clear main suspect, not suggested by anyone in this otherwise very rich thread. That is: 1) the Atlas showed increased signs of woofer pumping, over some months. Abnormal, when comparing to the Clavis and Titan. 2) For a short period, the diamond was half-loose from the cantilever, with blurred sound. 3) Next, it broke off, from the cantilever (this happened through normal, careful handling)  All this points to a gradually increasing defect in the diamond / cantilever connection. Assuming that a potential crack or breakup can indeed give some strange bass / subsonic pumping effects at first. I am no engineer, but it seems highly possible, and fits the data in my case.

I thank you all for all suggestions in this thread. My problem of woofer pumping is 'solved'. No diamond, no pumping. No woman no cry. Maybe, it was mainly a result of usage. It has 1200 or 1300 hours use, in my estimate. I will try to fix the Atlas. But this thread is now at rest from my side, since the problem is gone.  

Update: I have got a replacement for the broken cartridge, and I am very happy with the performance.

Some testing: The new Atlas makes it clearer that the subsonic effects (and possibly, the subsonic woofer pumping once per revolution) is part of the intended sound, e g in the introduction to Pink Floyd: Echoes. It resides in the recording (or my pressing) and is not in a fault in the system, even if the resonance frequency of my arm and cart is a bit low / challenging, so everything happening down at the end of the frequency scale is picked up.

I don’t hear much rumble or other unwanted effects, just a marvellous big soundscape.

On Rickie Lee Jones The evening, I no longer see any clear subsonic woofer pumping, just a lot of energy, in the woofers, coherent with what I hear.

So it seems, especially with the new Atlas - just look away from eventual woofer pumping (as long as the woofers don’t complain), give it a go, and enjoy the superior sound.

Pink Floyd’s Echoes is known to include "subsonic" effects. Maybe once per revolution - like they later experimented with heartbeats, on Dark side...or maybe on Echoes this is a not intended side effect, who knows. I have an early second pressing of the Meddle UK original, matrix side 2 (with Echoes): "SHVL 795 B-6" "11"? "1" and handwritten "HTM". HTM means Harry T Moss cutter extraordinaire at EMI UK. I have read that subsonic effects may happen due to record warp, but I cannot find any signs of this, with my copy.

Does it sound good? You bet!

Holter, The SME V is too light for the Lyra Atlas, a cartridge of intermediate compliance. I suspect you are seeing the woofer take off up between 15 and 20 Hz. Add one or two grams to the head shell and let us know what happens. 

Get a test record with vertical and lateral resonance test tracks and see what happens.